1. Field of the Invention
The present invention relates to a reverse inhibitor mechanism for regulating a gear shifting operation of an automatic transmission. More particularly, the present invention relates to a method of assembling the reverse inhibitor mechanism.
2. Description of the Background Art
There are several known reverse inhibitor mechanisms which regulate gear shifting operation of an automatic transmission. An example of such reverse inhibitor mechanism is disclosed in Japanese published patent document JP-A No. 2004-36584.
According to the Japanese published patent document JP-A No. 2004-36584, as shown in FIG. 8 thereof, a shift drum is rotatably journaled between opposing front and rear side walls of a transmission case. A reverse inhibitor groove is formed in a shaft end portion of the shift drum. A distal end portion of a reverse inhibitor arm is detachably engaged with the reverse inhibitor groove. The shift drum protrudes rearwardly from the rear side wall of the transmission case.
The reverse inhibitor arm has a proximal end portion fitted with a reverse inhibitor shaft. The reverse shaft is rotatably journaled to a rear side wall of the transmission case and a rear case cover of a power unit. The reverse inhibitor arm is urged by a spring in the direction where the distal end portion is engaged with the reverse inhibitor groove of the shift drum.
When the reverse is not set, i.e., when the transmission gear is not set in a reverse position, the distal end portion of the reverse inhibitor arm is engaged with the reverse inhibitor groove by the spring. Upon shifting (changing) of gears during the normal forward traveling operation, except the reverse (backward traveling operation), the reverse inhibitor arm is engaged with the reverse inhibiting groove to regulate the rotation of the shift drum, thereby inhibiting setting of the reverse rotation angle (setting the reverse).
Upon selection of the reverse position, the reverse inhibitor shaft is rotated to swing the reverse inhibitor arm against the force of the spring so as to be disengaged from the reverse inhibitor groove. This makes it possible to set the reverse rotation angle of the shift drum.
The reverse inhibitor mechanism is configured to have its reverse inhibitor shaft together with the reverse inhibitor arm disposed outside the transmission case, i.e., the reverse inhibitor mechanism is situated at the rear side wall of the transmission case and the rear case cover.
Assembling of the reverse inhibitor mechanism according to the Japanese published patent document JP-A No. 2004-36584 includes penetrating the bearing portion of the rear case cover by the rear end portion of the reverse inhibitor shaft, when the rear case cover is applied for covering in the state where the front end of the reverse inhibitor shaft is fitted with the bearing portion of the rear side wall of the transmission case.
Alternatively, assembly of the reverse inhibitor mechanism is performed by fitting the front end portion of the reverse inhibitor shaft with the bearing portion of the rear side wall of the transmission case while penetrating the rear end portion of the reverse inhibitor shaft into the bearing portion of the rear case cover. That is, the reverse inhibitor shaft is fixed at two positions, the front end in the rear side wall and the rear end in the rear case cover.
The temporary assembled state where one end portion of the reverse inhibitor shaft is journaled to the bearing portion is unstable because the only shaft end portion is supported. It is not easy to insert the other end portion of the reverse inhibitor shaft into the predetermined bearing portion by coinciding with the center of the shaft while engaging the reverse inhibitor arm with the reverse inhibitor groove for covering the rear side wall of the transmission case with the rear case cover. This may occasionally cause the reverse inhibitor shaft to be disengaged in contact with certain elements, and the reverse inhibitor shaft may fall off.
The reverse inhibitor arm is disposed outside the transmission case, and the reverse inhibitor groove in engagement with the reverse inhibitor arm is further formed in the outer side of the bearing portion of the shift drum, which may enlarge the shift drum itself.
Therefore, system and assembling method for the reverse inhibitor mechanism is required to be improved while compacting the size of the shift drum. In view of the above-described points, it is an object of the present invention to provide a reverse inhibitor mechanism of a transmission, which improves the assembly workability and reduces the size of the shift drum.